Two files are used to build the Docker image: Dockerfile and .dockerignore. The former provides all the build instructions while the latter provides the list of files/directories that should not be copied to the Docker image.

In order to make the Docker image clean, remove all auto generated files from the root of your workspace first. It is strongly recommeneded to simply pull a new one from GitHub/OPenStack. Specify the image name and the tag, and feed them to docker build.
The tag should be an existing git tag for the vmtp repository.